1. Field of the Invention
This invention relates to navigation, specifically to determining and presenting guidance information to a user traveling off-road.
2. Discussion of Prior Art
There are countless situations in which individuals are required to navigate an area that has neither roads nor street signs. Everyday, soldiers navigate battlefields, geocachers survey parks, and hikers traverse campgrounds. U.S. Pat. No. 6,963,800 to Milbert discloses a system for generating off-road routes, but there is currently no adequate system for intuitively guiding individuals along these off-road routes.
There are many systems which can provide turn-by-turn guidance to direct a user along a route which follows existing roads and streets. Such systems generally offer detailed auditory or visual information directing users towards their destination, often including natural language instructions. Prior to the present invention, existing systems which have attempted to provide analogous functionality in the off-road case have each suffered from a number of disadvantages. Before discussing these systems, we will begin with a brief description of on-road navigation systems.
On-Road Navigation
Commercial entities have enjoyed considerable success developing systems to guide users along routes which follow existing roadways. One popular example is the Hertz NeverLost™ vehicle navigation system, which notifies users as they approach each turn on their route. Hertz NeverLost also provides natural language auditory messages indicating the distance and direction of the turn and includes a three-dimensional arrow which allows the user to visualize the turn direction.
There have been a number of patents for systems which are similar to Hertz NeverLost™. For example:
U.S. Pat. No. 6,577,950 to Shimazu discloses a low-cpu system for on-road navigation.
U.S. Pat. No. 5,736,941 to Schulte et. al. discloses a system for on-road navigation which offers verbal commands.
U.S. Pat. No. 6,466,868 to Sakashita discloses a system for on-road navigation which is able to handle branching intersections in a more user-friendly way.
Existing Off-Road Systems
Various attempts were made to develop off-road guidance systems, although such systems have been fairly limited in comparison to on-road systems. The simplest solution for navigating a user off-road is to simply display an off-road route overlaid with the user's location without offering further guidance information. For example:
U.S. Pat. No. 6,356,837 to Yokota et. al. discloses a system which overlays off-road routes with the user's location on a display screen. The off-road routes are recorded during previous off-road trips taken by the user.
U.S. Pat. No. 6,519,528 to Endo et. al. discloses a system which overlays user-location onto a map. This system handles the on-road case as well and automatically detects when a user has left the road system, such as by entering a parking lot.
Fortunately, inventors have developed a number of off-road systems which are able to offer significantly more useful guidance information than the above methods. This is generally accomplished by directing users towards a series of intermediate waypoints. In order to guide users along a route, information is displayed indicating the direction and distance to the current waypoint. Once users are satisfied that they have reached a given waypoint, they can choose to move on to the next waypoint. An example system of this type is given by:
U.S. Pat. No. 6,751,551 to Katayama et. al. discloses a system which displays an arrow to guide a user along an off-road path. The primary claim of this system is that it offers a small display area suitable to smaller vehicles such as all-terrain vehicles (ATVs). The user presses a button to begin heading towards the next waypoint.
It is far from ideal to require the user to choose each successive waypoint along a route by hand, since this takes time and distracts the user's attention. To remedy this issue, systems have been developed which automatically assign the next waypoint by detecting when the current waypoint has been reached. This is generally accomplished by assigning a threshold radius around each waypoint. Once the user is within the threshold distance of the current waypoint, the system reassigns the current waypoint to be the next waypoint on the route. For example:
U.S. Pat. No. 6,836,725 to Millington et. al. discloses a system which uses fixed waypoints to guide a user off-road. The system provides directional arrows and non-verbal audible cues indicating that the current waypoint has been reached (to within a threshold radius).
U.S. Pat. No. 5,543,802 to Villevielle et. al. discloses a static waypoint system of which the primary claim is the ability to reverse routes, so that users may return to their starting point.
U.S. Pat. No. 5,646,855 to Jones et. al. discloses a system which also uses fixed waypoints to guide the user. This method uses a slight variant of the more typical waypoint methods described above. In particular, instead of directing users directly towards a waypoint, they are directed towards the perimeter of a circle centered at the waypoint. This allows users to avoid physical waypoints such as buoys.
While these systems are an improvement over methods which require manual intervention to set the current waypoint, they still have a number of disadvantages due to the fact that they rely on fixed waypoint locations and arbitrary threshold distances around each waypoint. These disadvantages will be discussed in more detail in the next section. In addition to these issues, a significant feature of existing on-road systems which has not yet been reproduced in off-road systems is user-notification as to the direction of the next turn in the route (i.e. turn-by-turn guidance). In particular, off-road systems generally focus solely on getting the user to the next waypoint and don't provide information about what direction the user will have to turn at the next waypoint (if a turn is required at all). One system which does attempt to offer such information is U.S. Pat. No. 6,751,551 to Katayama et. al., which displays both the direction to the current waypoint and also the direction of the next turn. However, this system is not completely off-road in the sense that for the purposes of providing turn information, it assumes that trail information is available. The turns are then given by the “crossing” and “branch” points (his terminology) in the trail.